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Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for primes by primitive root
pr=21; Select[Prime[Range], MultiplicativeOrder[pr, # ] == #-1 &]
Sequence in context: A041451 A268492 A130112 * A155025 A191068 A069690
Adjacent sequences: A019345 A019346 A019347 * A019349 A019350 A019351
David W. Wilson